Plate clamping mechanism



April 30, 1929. w. DURRANT I PLATE CLAMPING'MECHANISM Filed Feb. 7, 1928 ATTRNEY Patented Apr. .30, 1929.

mm. STATES WILLIAM D U'RRANT, OF PLAI'NFIELD, NEW JERSEY.

' PLATE GLAMPING MECHANISM.

Application'filed February 7, 1928. Serial no. 52,462.

My invention relates to improvements in plate clamping mechanisms for clamping printing plates on printing presses andis par-.

usually several such pairs on a single cylinder. In onewell-lmown type of vplateclamping mechanism, instead of using separate. clips at the Outer margin of the cylinder to clampthe plate, a single clip is used for each semi-cylindrical plate, this clip being bowed and extending substantially around half the circumference of the cylinder. Each bowed clip is supported on three slide blocks which slide in suitable ways formed in the cylinder. The central slide block is threaded to receive an adjusting screw and, by turning this screw, the bowed clip is moved forward into clamping position. Thus'it is possible to clamp the plate in positionby the operation of a single screw, whereas, prior to the use of this clamping means, separate adjusting screws are used on each slide block, for each slide block carried its own clip. d 1

While the construction described above has proved very serviceable and is Widely used, there are certain disadvantages inherent in this form of clamping mechanism which it is an object of the'pr'esen-t invention to overcome. v V v The stereotype metal plates when applied to the cylinder are apt to be stressed 'or strained and while the press is running the plates will automaticallyyield to these strains and re-adjust themselves. This is particularly true in high-speed presses where a very high centrifugal force is exerted upon the plates. Occasionally as a result of such readj ustment, the plate works loose from the holding clips. When this happens, the plate flies off the cylinder centrifugally, usually causing serious damage to property, if not to lifeand limb. To overcome this danger, I have devised a very simple mechanism which is applicable to existing pressures at a minimum of cost, whereby the bowed clip is not rigidly held against the edge of the stereotype plate,'but is pressed thereagainst by a certain amount ofspring pressure. This takes up any slack due to readjustment of the stereotype plate and keeps the clip always in engagement'with the plate. Other objects of my invention will appear hereinafter and the novelty and scope of my invention will be defined in the claims. d

In the accompanying drawings, Fig. 1 isa front elevation of a'porticn of a press cylinder showing my improved plate clampingmechanism applied thereto;

Fig. 2 is a plan view of thesame partly in section, the section being taken generally along the line 22 of F ig; 1; and

Fig. 8 is a fragmentary view in longitudinal section taken along the line 3-3 of Fig. 2.

In the drawings 1 use the reference numeral 10 to indicate a press cylinder on which is clamped a stereotype plate 11. The stereotype plate is formcd with a beveled edge 13 at each end thereof. Formed in the cylinder 10 are under-cut ways 14: which extend longi tudinally of the cylinder.

The present invention is not concerned with the method of securing the inner edge of the stereotype plate, and it will be understood that this may be done in any well-known manner; that is, on a cylinder on which four pairs of opposed stereotype plates are mounted, the inner plates will bear against a fixed ring formed on the cylinder while the outer end of each inner plate 1.1 and. the inner end of each outer plate 11 will be engaged by sliding clips 16 supported on blocks'sliding in the ways 14. There are three. sets of ways l t-on each diametrically opposed half of the cylinder. The outer pair of ways are fitted with slide blocks 15 while the central way is fitted with a block 17 which differs from the blocks 15 in beingconsiderably longer. A bowed clip 18 formed with an under-cut beveled inner edge is rigidly secured to the blocks 15 and 17. The block 17 is formed with a longitudinal bore which is tapped to re- 'ceive a feed screw 19. j The latter is mounted to turn in a journal box or thrust bearing 20 and is formed with a thrust collar 21 which lies in'a countersunk portion of thejournal box. Fitted into the countersunk portion of the journal box is a washer 22 which bears against the outer face of the thrust collar 21. A pin 23 serves to prevent the washer 22 from turning in the journal box 20.

There is nothing new in the parts so fa described and they represent standard practice. The novelty oi? my present invention lies in the attachment or the journal box 20 to the cylinder of the press. Ordinarily this box is rigidly attached to the outer face of the cylinder by means of bolts or machine screws. Instead of fastening the ournal box in this way, I ream out or enlarge part of each bolt hole 24L in the joinrnal box to form a seat 2 L for a heavy spring 25. Ilolts 26 are then iassed through the bolt holes and are titted with washers 27 which bear against the outer ends of spri s 253. The bolts 26 are shouldered at their inner ends to seat against the face of the cylinder and are formed with reduced threaded portions 28 which are threaded into tapped openings in the "face oi? the cylinder. Thus, there is a limit to which the bolts may be threaded into the cylinder and, by turning them up, a certain predetermined spring pressure is exerted upon the block 20.

In practice, the clamping mechanism is used as heretofore. In applying a plate to the cylinder, the plate is inserted between the interior clips 16 and the outer bowed clip 18. Then the screw 19 is turned by applying a wrench to the headed end 29 thereol, which will. feed the block 17 in "21rd and force the under-cut edge of the rim 18 against the tapered edge oi? the stereotype plate 11. The screw should be turned until the ournal box 20 has been forced away from the end face of: the cylinder and the springs 25 are completely collapsed. The thrust oi? the ring clip is thus taken by the springs 25 and they are designed to give sufiicient pressure for all purposes. 7 hen the press is running and the plate 11 adjusts itself to the various strains to which it is imposed, any shrinkage of the plate or any adjustment which would reduce the normal spacing between the inner clips and the outer ring clip will be compensated for by the springs 25. Thus, by a very simple expedient, I have provided a safety lock which may be applied readily and at a minimum of expense to existing presses, and which also may be used as a standard equipment for new presses.

Having thus described my invention, what I claim and desire to secure by Letters Patcut is:

1. In combiimtion with, a printing plate support, a clip adjustable along said support, a screw for feeding the clip, a thrust bearing for said screw, and means for securing the thrust bearing yieldingly to the support.

2. In combination with a printing plate support, a clip adjustable alon said support, a screw for feeding the clip, a thrust bearing for said screw, and resilient means for securing the thrust bearing to the support in position to yield to the thrust of the screw.

8. In combination with. a printing cylinder, a clip adjust-able along said cylinder, a screw for feeding the clip, a journal box providing a thrust bearing for the screw, and means for securing the journal box yieldingly to the cylinder.

4:. In combination with a printing plate support having under-cut ways therein, a plurality of slides mounted to travel in said ways, a clip secured to said slides, a screw for moving the clip and slides simultaneously tor-ward, a journal box providing a thrust hearing for the screw, and means for securing the journal box yieldingly to said support.

5. In combination with a printing cylinder having under-cut ways therein, a plurality of slides mounted to travel in said ways, a bowed clip secured to said slides, a screw for moving the clip and slides simultaneously forward, a journal box providing athrust bearing for the screw, and means for securing the journal box yieldingly to said cylinder. 1

6. In combination with a printing cylinder having under-cut ways therein, a plurality of slides mounted to travel in saidways, a bowed clip secured to said slides, a screw for moving the clip and slides simultaneously forward, a journal box providing a thrust bearing for the screw, and a spring adapted to press the journal box toward the cylinder against the thrust of the screw.

7 In combination with a printing cylinder having under-cut ways therein, a plurality of slides mounted to travel in said ways, a bowed clip secured to said slides, an adjusting screw for moving the clip and slides simultaneously along the cylinder, a journal box providing a thrust bearing for the screw, the journal box being mounted on the cylinder and capable of limited movement relative thereto, and a spring adapted to resist such movement.

8. In combination with a printing cylinder having under-cut ways therein, a plurality of slides mounted to travel in said Ways, a bowed clip secured to said slides, an adjusting screw for moving the clip and slides simultaneously along the cylinder, a journal box providing a thrust bearing for the screw, the journal box being formed with bolt holes, each hole having a shoulder formed therein, a com pression spring in each bolt hole bearing at its inner end against said shoulder, a bolt extending through each bolt hole and threaded into the cylinder, and a. shouldered part on the bolt bearing against the outer end of the spring.

9. In combination with a printing cylinder having under-cut ways therein, a plurality of slides mounted to travel in said ways, a bowed clip secured to said slides, an adjusting screw for moving the clip and slides simultaneously along the cylinder, a journal box providing a thrust bearing for the screw, the journal box being formed With bolt holes, each hole having a shoulder formed therein, a compression spring in each bolt hole bearing at its inner end against said shoulder, a bolt extending through each bolt hole and threaded into the cylinder, a shouldered part on the bolt bearing against the outer end of the extent to which it may be threaded into the cylinder.

In testimony whereof, I have signed this specification.

WILLIAM DURRANT. 

